Inflammatory response and the subsequent fibrous capsule formation are often used as a screening method to determine biocompatibility of an implanted material. In this study, porous implants of tricalcium phosphate-lysine (TCPL) delivery devices were implanted intraperitoneally (i.p.) and subcutaneously (s.c.) using adult male rats as a model. The fibrous capsule surrounding the implant was studied histochemically to determine the resorbability rate of the devices. Fibrous capsular tissues were carefully dissected away from the capsule noting the tissue closest to the implanted material. Evaluation of the sections (5um, H&E) collected from various areas of the implants (n = 15 per group) revealed that: (1) regardless of the site of surgical implantation, all devices were encapsulated with fibrous tissue within three days post implantation and the thickness of the capsular tissue was found to be directly proportional to duration of implantation, (2) the thickness of fibrous tissues collected from i.p. site were significantly higher than those collected from s.c. site of implantation, (3) vascularity, macrophages, multinucleated giant cells and plasma cells at the TCPL implant-interface were evident after the first week, and the persistence of these cell types and progressive angiogenesis in subsequent weeks was apparent. The formation of distinct cell layers was remarkable in the fifth week phase, (4) SEM and radiographic analysis of retrieved devices showed a significant (P < 0.05) increase in the number of macropores (12 to 36 um2) in TCPL devices implanted s.c. than the number of macropores in TCPL devices implanted i.p. The mechanism of biodegradation process in an in vivo environment is not fully elucidated. This observation and previous observations led us to suggest that the site of surgical implantation is an instrumental key in designing TCPL delivery system.